We have a list of playbooks on the doc site that has not been super well maintained, and I know people have been doing lots of GREAT things lately and would like to mention them:
http://ansible.cc/docs/contrib.html
If you would like to add something, send a pull request to this file:
https://github.com/ansible/ansible/blob/devel/docsite/latest/rst/contrib.rst
Similarly, if you write a module and I have for some reason not included that in core, we are happy to mention modules here.
If you have something to share with the community, this is a great place to archive it.